Abstract: A method of closed loop control for an optical link is presented, utilizing a copper feedback connection between the optical transmitter and optical receiver, suitable for short distance applications. An architecture is provides that may be used to define and maintain an optimum optical launch power for a defined bit error rate, guaranteeing extinction ratio and absolute optimum operating power. The invention also includes the use of such a loop in achieving fast link initialization and dynamic optimization to compensate for all effects of time and temperature for all components within the link.

Abstract: A method of closed loop control for an optical link is presented, utilizing a copper feedback connection between the optical transmitter and optical receiver, suitable for short distance applications. An architecture is provides that may be used to define and maintain an optimum optical launch power for a defined bit error rate, guaranteeing extinction ratio and absolute optimum operating power. The invention also includes the use of such a loop in achieving fast link initialization and dynamic optimization to compensate for all effects of time and temperature for all components within the link.

Abstract: A direction sensitive energy detecting apparatus characterized by having a pair of energy receiving and transmitting devices of different polar characteristics and so disposed that they define together one end of a path in such a way as to be coincident with each other; with the sensor being adapted to give two first outputs at least one of which is variable as a function of the direction of the path and the detector having ratiometric means for generating a second output which is a function of the ratio of the two first outputs and is variable only in response to changes in direction.

Abstract: A proximity detector in which a sensor unit (10) senses reflected energy received from a predetermined volume or zone and generates an electrical signal representative of the received energy. Circuit means process the received signals to control the operation of apparatus such as automatic doors. One aspect of the invention is concerned with the sensor unit in which transmitters (14) are located in a housing with a receiver (15). The housing has a filter (7) through which infrared radiation can be transmitted and received. Mask areas on the filter define the zone into which radiation can be transmitted and from which it can be received. The filter is interchangeable so that zones of different sizes and dimensions can be provided. Another aspect is concerned with novel signal processing circuitry and a further aspect is concerned with an ultrasonic system wherein a multiplier is used to process the received signals.

Abstract: A movable door incorporates a proximity detection system for sensing obstructions in the path of the door. The system comprises an array of transmitter/receiver pairs (21, 22 and 23), each pair comprising a transmitter (1) for transmitting an energy pulse, a receiver (2) located adjacent the transmitter and directed to receive any reflected transmitter pulses, and a shielding (3) for shielding the receiver (2) from receiving energy pulses directly from the transmitter (1). At least two transmitter/receiver pairs (21, 23) are mounted on a leading edge or face of the door (12) to transmit energy pulses in a direction which is not at right angles to the leading surface or edge of the door, to monitor for obstructions in the path of the door (12). Another two transmitter/receiver pairs (26 and 28) are mounted on the leading edge or surface of the door (12) to transmit energy pulses at right angles to the surface or edge of the door (12).

Abstract: A movable door incorporates a proximity detection system for sensing obstructions in the path of the door. The system comprises an array of transmitter/receiver pairs, each pair comprising a transmitter for tranmitting an energy pulse, a receiver located adjacent the transmitter and directed to receive any reflected transmitter pulses, and a shielding for shielding the receiver from receiving energy pulses directly from the transmitter. At least two transmitter/receiver pairs are mounted on a leading edge or face of the door to transmit energy pulses in a direction which is not at right angles to the leading surface or edge of the door, to monitor for obstructions in the path of the door. Another two transmitter/receiver pairs are mounted on the leading edge or surface of the door to transmit energy pulses at right angles to the surface or edge of the door. Different transmitter/receiver pairs may transmit on different frequencies, and means for suppressing unwanted reflected signals is provided.

Abstract: A system for synchronizing pulse signals transmitted between two stations using only two conductor lines includes a synchronization circuit. The circuit includes two modulators and two EXCLUSIVE-OR gates for controlling when data pulses are transmitted and when synchronization pulses are transmitted.

Abstract: A detection system for a sliding lift or elevator door comprises at least two sensors for monitoring the door opening. The sensors are arranged to detect the presence of a moving irregular shape (e.g. human form) in the doorway to reverse the opening action of the door or, if already open, to prevent the door from closing. A signal compensation circuit is provided to process the output signals from the sensors in a sense to maintain the outputs equal under steady state conditions. This is achieved by using the output of a first sensor as a reference signal. A comparator compares the output of a second sensor with a reference signal and through a feedback loop modifies the output of the said second sensor in a sense to equal the output of the first sensor. The feedback loop contains a delay circuit which is switchable between a long and a short delay. For slow changes in the output of the second sensor the long delay is effective but for first changes the delay circuit is switched to provide a short delay.